An impedance CT system employs the fact that media have individual electric impedance values, to find spatial distributions of media in a three-dimensional object. The impedance CT system passes a current through an object, measures a potential distribution induced at the surface of the object, and visualizes an impedance distribution inside the object according to the potential distribution. The system is applicable to measure the distributions of blood, lungs, fat, etc., in a human body as described in a bulletin Bio Medical Engineering (BME) Vol. 8, No. 8 (1994), p. 49, issued by Japanese Society for Medical and Biological Engineering.
In addition to the impedance CT system, there are other apparatuses to measure electric impedance values and find subcutaneous and visceral fat quantities. An example of such apparatuses is a body fat measuring apparatus disclosed in Japanese Patent Laid Open Publication No. 11-113870 (referred to as “related art 1”). Another example is an internal fat measuring instrument disclosed in Japanese Patent Laid Open Publication No. 11-123182 (referred to as “related art 2”). The related art 1 attaches a plurality of electrodes to the surface of a subject (human), measures impedance values among the electrodes, and creates an impedance matrix for a cross section of the subject defined by the attached electrodes. An operation unit of the related art 1 calculates the product of the impedance matrix and a coefficient matrix prepared from information on the electrodes attached part of the subject entered through an input unit, and according to the product, provides a cross sectional body fat distribution of the subject. The related art 2 winds a belt around the body of a subject. The inside of the belt has electrode pairs each consisting of a current path forming electrode and a measuring electrode. The electrode pairs are arranged substantially at regular intervals. Two electrode pairs are chosen, and an AC current is passed between the current path forming electrodes of the chosen electrode pairs, to form a current path. The measuring electrodes measure an impedance value in the current path. The two electrode pairs are properly chosen so that adjacent electrodes may mainly measure subcutaneous fat and opposing electrodes may mainly measure visceral fat.